Group III-P semiconductor devices such as (AlxGa1−x)1−yInyP light emitting diodes (LEDs) are used to produce visible wavelengths from red to amber. AlInGaP LEDs are typically formed by growing epitaxial layers, including p-type and n-type layers sandwiching a light-emitting active layer, on a GaAs growth substrate. High quality ternary and quaternary substrates are very difficult to fabricate, so GaAs substrates are commonly used. To produce low-defect LED layers, the lattice constant of the (AlxGa1−x)1−yInyP epitaxial layers must match the lattice constant of the GaAs. To match the GaAs lattice constant, y=0.48. The x value is adjusted to achieve the desired emission wavelength.
A flip chip III-P LED described in U.S. Pat. No. 7,244,630 is illustrated in FIG. 1. A lower confining layer 22 of n-type AlInP is grown on a growth substrate (not shown). The AlInP confining layer 22 has a band gap that is higher than the band gap of the active layer. An active layer 24 of (AlxGa1−x)0.47In0.53P, which may comprise a plurality of layers, is grown over the confining layer 22. A p-type upper confining layer 26 of AlInP is grown over the active layer 24. A highly doped p-type AlInGaP contact layer 71 may be provided over layer 26. Layers 24, 26, and 71 are etched to expose the n-AlInP confining layer 22 for electrical contact. A metal n-electrode 83 is then formed to electrically contact the n-AlInP confining layer 22, and a p-electrode 84 is formed to contact the p+ AlInGaP layer 71.
The p and n-electrodes are bonded to metal pads on the package element 87. The substrate may be removed after bonding the electrodes to the package element 87. Vias electrically couple the metal pads on the top of package element 87 to p- and n-electrodes 90, 91 on the bottom of package element 87. Electrodes 90, 91 may be soldered to pads on a circuit board or to pads on another package.
The top surface of the LED (the n-AlInP layer 22 in the example) is further processed to have light extraction features 92. Such features may include roughening or other techniques, such as ordered texturing or a photonic crystal structure, to increase the light output.